Some Protozoa use pseudopodia (sing. pseudopodium) as locomotory organs. These structures, which may occur as thick  lobopodia or as fine  filopodia (Fig. 1, Pellicle/Fig. 1), are produced by the cytoplasmic movement mediated by the activity of the Ca2+-regulated actin-myosin complexes ( Cytoskeleton). The contraction of filaments of actin-myosin causes pressure on the  cytoplasm at the posterior pole and this initiates a forward flow of the cytoplasm at the apical pole. At the apical pole the ameboid movement is enhanced by a transformation of the local cytoplasm from a stable gel-form to a more liquid sol-form. Pseudopodia are most prominent in the various types of  amoebae but may also be found in motile metazoan cells such as leucocytes or in nematode sperms ( Nematodes/Reproductive Organs).

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